Experiment One: Introduction to the Lab Volt Test Equipment
Objective: To train the student on the use of the Lab Volt Equipment.
Equipment: Lab Volt Test Station
LVDAM-EMS 2.0 Software
An Overview of the Lab Volt Test Equipment
The Lab Volt test station consists of a Data Interface Module, a Power Supply Module,
Resistor, Capacitor, Inductor, and motor modules.
Data Interface Module
The Data Interface module is connected to a computer and runs under LVDAM-EMS
software. The Data Interface module is powered by connecting 24 V AC to the Low Power
Interface port. The Data Interface module has three ports for measuring volts labeled E1,
E2, E3 and three ports for measuring current, I1, I2, and I3. These ports are placed in a circuit
the same way a multimeter would be used to take measurements. Voltage measurements
are taken across the circuit component whereas the circuit is routed through the ports for
current measurements. The ports labeled T, N, and neutral on the module connect to the
Prime/Dynamometer to record speed (N) and Torque (T)
Power Supply
The Power Supply module has two three-phase AC supplies and two DC supplies needed
for test purposes. One of the AC and one of the DC supplies are variable; the other supplies
are of a fixed voltage. The variable supplies are labeled 0-120V and are controlled by the 0100 Dial. The Power Supply module also has an analog meter displaying the output of the
supply selected by the dial labeled AC (4-5, 5-6, 4-N, 5-N, 6-N), DC (7-N, 8-N). The
Power supplies are turned on or off by the one 1/0 Power switch. The 24-3A-AC has a
separate power switch.
Impedance modules
Resistor, capacitor and inductor modules have three groups of three parallel fixed
impedances. Jumpers are needed to place each group in the circuit then the 1/0 toggle
switch placed in the 1 position activates the individual impedances within the group.
Motor modules will be discussed in later labs.
The LVDAM-EMS software
Selecting the LVDAM icon on the desktop or selecting it under programs can activate the
software. There are four analyzing modes to choose from Harmonic analyzer, Metering,
Oscilloscope, and Phasor analyzer. Double click the metering option and then select the
acquisition option. The metering mode will display a page of meters showing volt, amp,
and power meters. The meters can be modified to display analog or digital, AC or DC, real
power (P), imaginary power (Q) or apparent power (S). If the meters do not appear to
display the correct values check to see that the Data Interface module has 24 V AC power.
To record data select the Data Record button from the toolbar. This will record all the
meter readings to a data table. To view this data table, select the Data Table button on the
Metering Screen. Once several records have been saved to the Data Table this table can
then be viewed graphically by selecting the Graph button. A graph grid will appear. The x
and y axis values must then be selected. For example select E1 for the y axis and I1 for the x
axis then press the Refresh button to display E1 verses I1 graphically. From the metering
page or by going back to the beginning page the other three analyzing modes can be
selected. You may save your data as an excel file which is easy to manipulate. The
Oscilloscope mode displays up to eight colors coded channels. The input to each channel is
selected from the input drop down box. Once the inputs are selected, push the Refresh
button to see the display. The phasor analyzer works in a similar manner.
Voltage, Current, and Power Measurements in DC and AC Circuits
The purpose of this exercise is to become familiar with LABVOLT training system and to
enhance students understanding of DC and AC circuits. In Part I a variable DC voltage is
connected to a resistive and voltage, current, and power are recorded. In Part II a variable
single phase ac voltage is connected to a passive and measurement of voltage, current and
power are taken. In Part III, a three phase supply is connected to a passive load to verify
phase and line relations illustrate three phase power calculations in delta and Y connected
loads. The relationship between phasor and time domain quantities is also observed and
recorded. The student will find that these modern digital equipment very powerful and
useful in understanding electrical machines and power system.
PART I:
Resistive DC circuit with a variable supply
Fig. 1: Resistive DC circuit with a variable supply
Procedures:
1. Set up the circuit shown in fig. 1 above using the Lab Volt test equipment. Set up
wattmeters P1 and P2 to measure the power out of the DC source and the parallel
resistors. Make sure that the wattmeters polarity is correct. Use an ohmmeter to
measure the equivalent resistance as seen by the DC source.
2. Open the LVDAM-EMS software and select the Metering option, then Acquisition. Be
sure the low voltage 24Vac power to the Data Interface Module is connected.
3. Vary the DC voltage source from 0 to 120 VDC in 20 V increments. In each step record
V1, V2, I1, I2, P1 and P2. The data in each increment is recorded by pressing the Record
button in the Metering screen toolbar. The recorded data can be viewed by pressing the
Data Table button. Once all the values are recorded they can be shown graphically by
pressing the Graph button. A graph grid will appear and the values for the x and y-axis
must be selected. To display the plot press the Refresh button on the Graph screen.
4. Produce a plot of V1 verses I1 and a second plot of V2 verses I2. The slope of the line
should compare to the equivalent resistance in the circuit, y = mx + b; where y =V, m =
R, x = I, b = 0; (V=IR). From the graphs determine the slopes and compare to the
calculated equivalent resistances.
5. Using basic circuit theory, calculate the expected values for V1, V2, I1, and I2 and
compare these to the measured values.
PART II:
Single phase AC circuit
Fig. 2: Single phase AC circuit
Procedures:
1. Set up the circuit shown in Fig. 2 using the Lab Volt test equipment. Also set up set up
wattmeter P1 and P2 to measure the real and reactive power Q supplied by the ac source
and the real power absorbed by the inductor. Make sure that meters polarity is correct.
Finally set up an Ohmmeter to measure the inductor resistance RL.
2. With the inductor set at 3.2 vary the resistor value from 0 to 3600 (0, 300, 600, 1200,
2400, 3600) by switching in and out various resistor combinations. In each step record
the currents I1, I2, I3, V1, V2, V3, P1, Q1, and P2 for each resistive value by selecting the
Record button in the Metering screen toolbar. Data can be viewed by pressing the Data
Table button. Note also how the Reactive (Q) and Apparent (S) power changes. The
metering display shows real values not complex values, the phasor display shows
complex values.
3. With the inductor set to 3.2H and the resistor value at 300 and 2400 Ω record an
oscilligraphic record of v1(t) and i1(t). Also record a phasor plot of V1 and I1. Note the
angle between the voltage and current. Also compare the magnitude of the phasor to the
peak value of the sinusoid.
4. With the inductor set at 0.8 H and the resistor at 600 ohms your assignment is to
improve the power factor by 5%. Check your design by calculating and measuring
power factor and the current I1, record the value of P, Q, and S before and after the
improvement.
Note: Adding a capacitor to the circuit can improve the power factor.
What is the value of the capacitance needed to achieve this improvement?
Change the capacitor value and watch Q and current magnitude and phase angle.
5. Using basic circuit theory, calculate the expected values for V1, V2, I1, and I2. Compare
these values to the measured ones.
Suggested report for Single Phase AC Circuit:
1. Compute the value of the of the inductor resistance RL. Compare this value to the
measured value.
2. For R = 300 in step 3 above find the power factor. Compute V1 I1*. Compare this value
to the measured P and Q. Also compare VIcosθ, VIsinθ , and VI(apparent power) to the
measured values
3. Compute the power factor using P and Q, and S. Also Compute the pf using R, X and
Z. Do not forget to include RL in all your calculations. How does it compare to the
power factor noted on the phasor diagram?
4. Using V1 and S (complex power) compute the impedance Z. Compare this value to the
one indicated on the circuit. Include RL in your calculations.
5. Draw the power triangle for this circuit.
6. From your data, prepare a single phasor diagram with V1 as a reference, showing the I1
phasors for all six values in step 2 above. On the same diagram draw V2. Do not forget
to include RL in your calculations.
7. In the discussion of your results include a brief discussion comparing the recorded
phasor diagrams to the oscilligraphic records. Also justify the phase angle difference
between the voltage and current phasors and the sine waves and the relationship
between the peak value of the sine wave and the length of the corresponding phasors.
PART III:
Three phase Circuits
The goal of this experiment is to verify the relationship between line and phase quantities
for a wye, Y and a delta, ∆ connected load.
WYE Connected Load
Connect the circuit as shown in Fig. 3. Refer to Fig. 2.3.1 of the text for the proper
connection diagram for Two-Wattmeter method of measuring three phase power. Note
both wattmeters use Vb as the reference. View and record the displays on the Metering
screen and Phasor analyzer.
Fig. 3: Three phase source, wye connected load
Suggested Report for a wye, Y Connected Load
1. Verify the relationship between phase and line voltages
2. Calculate Ian, the load current and compare it with the line current Ia.
3. Calculate the power factor (specify lead or lag) and compare to the measured
value(phasor diagram)
4. Calculate the power(Real, reactive, complex, and apparent) using line quantities
5. Repeat step 3 using phase quantities
6. Compare 3 and 4 with the measured values
7. From step 3 or 4 calculate the load impedance. Compare this with the measured or
stated values. (Note that the resistance of the 3.2 H should be included in your
calculations.)
Delta connected load
Connect the circuit as shown in Fig. 4(compare this to that shown in Fig. 3). View and
record the displays on the Metering screen and Phasor analyzer. The total three phase
power supplied to the load can be computed as the sum of the values of the two wattmeters.
Compare the power used by delta load to the wye load.
Fig. 4: Three phase source connected to a delta load.
Suggested Report for a delta, ∆ connected load
1. Repeat step 1 through 6 above
2. Find the ratio of the load power absorbed when the system is connected in wye to the
load when connected in a delta.
3. Examine the oscilligraphic and phasor records for both wye and delta loads
Table of Contents
I.
Part I: .................................................................................................................................................... 4
II.
Part II: ................................................................................................................................................. 6
III. Purpose………………………………………………………………………………………………………...4
IIII. Equipment…………………………………………………………………………………………………….4
V. Outline……………………………………………………………………………………………………………4
IV. Procedure……………………………………………………………………………………………………….4
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List of Figures and Tables
I. Figure 1………………………………………………………………………………………………………..3
II. Figure 2……………………………………………………………………………………………………......4
III. Figure 3……………………………………………………………………………………………………….5
IIII. Equation 1, straight line equation.………………………………………………………………..4
V.
Equation 2, Ohms law………………………………….………………………………………………4
IV. Equation 3, Power factor……………………………………………………………………….…….6
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Purpose: Educate and familiarize students with lab volt test
station
Equipment: LVDAM-EMS 2.0 software
Outline:
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Connect circuit in lab volt test equipment
Measure values using the software
Increment 20 v for 0 to 120 v
Record all data in table
Plot V1 and I1
Plot V2 and I2
Calculate using circuit analysis
Re-do the same for part two;
Utilize inductive
Power factor by 5%
Procedure:
I.
Part I:
1. Construct resistive DC circuit
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Figure1: resistive DC circuit with
variable supply
V1 and I1
2. Display the two plots
mentioned in outline
V2 and I2
5
3. Use
Y = mx+b
(1)
and
V=IR
to determine the slope from the graph
4. Expected values
V1, V2, I1 and I2
Comparison
II.
(2)
Part II:
1. Construct single phase AC circuit
Figure2: single phase AC circuit
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2. Set P1 and P2 to measure Q, and use Ohmmeter to measure
the inductor of resistance RL.
3. Record I1, I2, I3, V1, V2, V3, Q1, P1, P2 at each incremented
resistor value while inductor on 3.2 H from 0 to 3600 (0,
300,
600,
1200,
2400,
3600)
4. Record V1(t) and I1(t) oscilligraphic along with the pharos
plot of V1 and I1. Set inductor on 3.2 H and resistor value
at 300 and 2400 Ohm’s.
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5. Improve power factor by 5% while inductor on 0.8 H and
resistor at 600 Ohm’s. Record P, Q and S before and after
the improvement.
Q
S
New Q
P
Figure3: Illustration for power factor
Xc=
1/2pi*f*c
(3)
6. Use circuit analysis to calculate V1, V2, I1 and I2
Comparison
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